In a silver halide color photographic material, a color image is formed when the material is exposed to light and then is subjected to color development so that an oxidized aromatic primary amine color developer and a dye-forming coupler (hereinafter referred to as coupler) may interact.
Generally, in such a process, the color reproduction method employed is a subtractive color process wherein to reproduce blue, green and red, a yellow color image, a magenta color image, and a cyan color image respectively complementary thereto are formed. To form a yellow color image, generally acylacetamide couplers and malondianilide couplers are used as a yellow dye-forming coupler (hereinafter referred to as yellow coupler); to form a magenta color image, generally, for example, 5-pyrazolone couplers and pyrazolotriazole couplers are used as a magenta coupler; and to form a cyan color image, generally phenol couplers and naphtol couplers are used as a cyan coupler.
Yellow dyes, magenta dyes, and cyan dyes obtained from these couplers are generally formed in silver halide emulsion layers or layers adjacent thereto having color sensitivities to radiations respectively complementary to the radiations that are absorbed by them.
As yellow couplers, particularly for forming images, acylacetamide couplers, represented by benzoylacetanilide couplers and pivaloylacetanilide couplers, are generally used. Since the former are generally high in coupling activity with the oxidized products of aromatic primary amine developers at the time of development and the yellow dyes formed are high in the molar extinction coefficient, they are used mainly in photographing color photographic materials that require a high sensitivity, particularly color negative films. On the other hand, the latter are excellent in the spectral absorption characteristics and fastness of the yellow dye and are mainly used in color papers and color reversal films.
However, although benzoylacetanilide-type couplers are high in coupling reactivity with the oxidized products of aromatic primary amine developers at the time of color development and they are great in the molar extinction coefficient of the yellow azomethine dye formed, they have a defect that they are poor in spectral absorption characteristics for the yellow image. Likewise, while pivaloylacetanilide-type couplers are excellent in the spectral absorption characteristics for the yellow image formed, they have defects in that their coupling reactivity with the oxidized products of aromatic primary amine developers at the time of color development is low and the molar extinction coefficient of the yellow azomethine dyes formed is small.
A high coupling reactivity of a coupler and a high molar extinction coefficient of a dye formed therewith make possible a high sensitivity, a high gamma value and a high color density, and bring about what is called a high color-forming property. Additionally, excellent spectral absorption characteristics in a yellow color image implies absorption characteristics such that, for example, the sharpness of the spectral absorption-curve on the long wavelength side is good and undesirable absorption in the green region is minimal.
Therefore, it is desired to develop yellow couplers having the advantages of both benzoylacetanilide-type and pivaloylacetanilide-type couplers, i.e., a high color-forming property (high coupling reactivity of the coupler and the high molar absorption coefficient of the dye) and spectral absorption characteristics which are excellent in the color image.
As acyl groups of acylacetamide-type couplers, for example, a pivaloyl group, a 7,7-dimethylnorbornane-1-carbonyl group, and a 1-methylcyclohexane-1-carbonyl group are disclosed in U.S. Pat. No. Re. 27,848 and, for example, a cyclopropane-1-carbonyl group and a cyclohexane-1-carbonyl group are disclosed in JP-A ("JP-A" means unexamined published Japanese patent application) No. 26133/1972. However, these couplers are poor in some points; for example, their coupling reactivity is poor, the molar extinction coefficient of the dyes is small, or the spectral absorption characteristics of the color images is poor.
A higher sensitivity, higher image quality, and higher toughness have been earnestly desired in recently developed photographic materials. Therefore, the development of couplers excellent in color-forming property and spectral absorption characteristics of the color image has been strongly pursued. However, prior yellow couplers including those disclosed in the above two patents, have had difficulty in satisfying all these requirements.